Coupling of a sensor elements to a transponder

ABSTRACT

The invention relates to the coupling of a sensor element to a transponder, the connection of said sensor element to the transponder being achieved by capacitive or inductive coupling. This enables any separation layer that may lie between the sensor element and the transponder to be retained, allowing the invention to be advantageously used in gas and liquid-tight containers, such as tyres. In addition, electrically non-conductive materials of the object to be measured can be used as a dielectric for the capacitive coupling and electrically conductive parts can form part of a conductor loop for the inductive coupling.

The invention relates to linking a sensor element with a transponder.

The wireless interrogation of the relevant electrical parameters of atransponder by means of a suitable reading device is a basic function ofradio sensory technology. The information about the physical parametersto be measured is impressed on the interrogated electrical parameters.

In various fields of application in which contactless measuring sensorsare used, the location at which the measurements are taken (by one ormore sensor elements) does not coincide with the proper transponderposition for radio interrogation by the read device. In this case, thesensor elements are generally wired to the other functional componentsof the transponder (particularly the units of the transponder which areconnected to the read device by radio).

In many applications, the sensor element (8) cannot be wired directly tothe transponder without interfering with the function of the measurementsubject owing to a functionally essential separating wall, membrane,coating, or suchlike between the transponder and the sensor, which wouldhave to be penetrated and therefore damaged.

The object of the invention is to provide a link of the type describedabove which does not interfere with the function of the measurementsubject.

This object is achieved both by realizing the link between the sensorelement and the transponder by means of capacitive coupling, and byrealizing the link between the sensor element and the transponder bymeans of inductive coupling.

Advantage is gained particularly through the use of a capacitor as thesensor element, whose value depends on the respective measurement.Alternatively, it can also be advantageous when an inductor or ohmicresistor whose value depends on the respective measurement is used asthe sensor element.

In applications having to do with measuring the thickness of a hollowbody, or in which the mechanical stability of the body cannot beinterfered with, a preferred development of the invention provides forthe link between the sensor element and the transponder to be realizedwithout mechanical penetration, either complete or partial, of aseparating layer between the transponder and the sensor element. Typicalexamples of such applications include automobile or airplane tires,henceforth simply tires.

An advantageous development of the invention provides that at least thesensor element or the transponder is disposed on opposite sides of aseparating layer. An alternative which is well suited to manyapplications provides that one of these elements is preferably disposedeither at the surface or in the interior of the separating layers.

A preferred application of the invention is measurement registration bythe sensor elements in an interior space of a container which is filledat least partly with gas or liquid.

When the separating layer consists of electrically insulating material,the capacitive coupling is particularly easy, the dielectric of saidcoupling being formed at least partly by the mechanical separatinglayer.

If there is an electrical conductor present in the separating layer, theinductive coupling is particularly easy in that at least part of aconductor loop of said coupling is formed by the existing conductor.

When the invention is used in a steel-belted tire, it is particularlyadvantageous for the belt to be used as the conductor loop of theinductive coupling.

Additionally or alternatively, it is expedient when a conductor loop isarranged in a tire through vulcanization.

Exemplifying embodiments of the invention will now be described withreference to the drawing. Shown are:

FIG. 1 a block circuit diagram of a first example of the linking of asensor element (8) with a transponder through capacitive coupling; and

FIG. 2 a block circuit diagram of a second example comprising inductivecoupling.

According to FIG. 1 a sensor element is wirelessly linked with atransponder 5; i.e., the sensor element 8 and the transponder 5 are notwired together. The output of the sensor element 8 is insteadcapacitively coupled with the input of the transponder 5 via a couplingcapacitor 7, 7′. The sensor element 8 can be designed as an ohmicresistor, a capacitor, or an inductor depending on the measured value.

The transponder 5 is connected via an antenna 6 to an antenna 4 of aseparate write/read device 1, which comprises a transmitter 2 and areceiver 3. Measurement data from the sensor element 8 can be readwirelessly by the write/read device 1. The write/read device 1 isstationary, whereas the sensor element 8 and the transponder 5 aresituated on a moving measurement subject 13.

In the example represented, the sensor element 8 and the transponder 5are separated by a membrane 9 or other electrically nonconductivematerial. The membrane 9 or other nonconductive material forms adielectric between the plates of the coupling capacitor 7, whichinfluences the coupling capacities.

This configuration occurs when the sensor element 8 is placed inside abody such as an airplane tire. In order to measure temperature,deformation, or other physical parameters using suitable sensor elementsin the tire carcass, one plate of the coupling capacitor 7 is arrangedon the inside of the tire, and the other plate is fully integrated intothe tire material at a defined distance from the first. The sealinginner layer of the tire remains uninjured. This is very important owingto the butyl layer that is applied here, because this is a criticaldeterminant of the density of the tire. The tire material between thecapacitor plates forms the dielectric of the coupling capacitor 7.

In this example, the write/read device 1 is arranged in a vehicle, andthe measurement data for the tire can be transmitted to an on-boardcomputer or suchlike during travel.

FIG. 2 represents an application in which the wireless linking of thesensor element 8 and the transponder 5 is achieved through inductivecoupling 12. Two coils 10, 11 are magnetically coupled with the aid ofthe constructional givens of the measurement subject. If theconfiguration is used in a tire, one of the coils 10 is situated insidethe tire, and the other coil 9 is integrated into the tire material. Thesecond coil can be formed at least partly by a steel belt.

For measurement purposes, any arbitrary physical quantity can be used;in other words, the concrete embodiment of the element which senses themeasurement value is not determinative and generally depends on whichparameters are sought. Possible embodiments of the sensor element 8include capacitors, inductors, and ohmic resistors whose value dependson the respective measurement.

1. Linking of a sensor element with a transponder, characterized in thatthe transponder (5) is linked with the sensor element (8) throughcapacitive coupling (7).
 2. Linking of a sensor element with atransponder, characterized in that the transponder (5) is linked withthe sensor element (8) through inductive coupling (12).
 3. Configurationaccording to claim 1 or 2, characterized in that a capacitor whose valuedepends on the respective measurement is used as the sensor element (8).4. Configuration according to claim 1 or 2, characterized in that aninductor whose value depends on the respective measurement is used asthe sensor element (8).
 5. Configuration according to claim 1 or 2,characterized in that an ohmic resistor whose value depends on therespective measurement is used as the sensor element (8). 6.Configuration according to claim 1 or 5, characterized in that thesensor element (8) is linked with the transponder (5) without aseparating layer between the transponder (5) and the sensor element (8)being partly mechanically penetrated.
 7. Configuration according toclaim 1 to 5, characterized in that the sensor element (8) is linkedwith the transponder (5) without a separating layer between thetransponder (5) and the sensor element (8) being completely mechanicallypenetrated.
 8. Configuration according to claim 1 to 7, characterized inthat the measurements are registered by sensor elements on the oppositesides, at the surface, or in the interior (i.e. in the material), ofseparating layers of any kind.
 9. Configuration according to claim 1 to7, characterized in that the measurements are registered by sensorelements in the interior of containers of any kind which are at leastpartly filled with gas or fluid.
 10. Configuration according to claim 1to 7, characterized in that the measurements are registered by sensorelements in the interior of wheels of any kind which are at least partlyfilled with gas or fluid.
 11. Configuration according to claim 1 to 7,characterized in that the measurements are registered by sensor elementson the surface or in the interior (i.e. in the material) of tires of anykind.
 12. Configuration according to claim 1 to 12 [sic], characterizedin that the dielectric which is required for capacitive coupling isrealized by the undamaged, that is to say at least not completelypenetrated, mechanical separating layer.
 13. Configuration according toclaim 1 to 12, characterized in that the inductive coupling is realizedwith the aid of a structure already in existence which is usable as anelectric conductor loop.
 14. Configuration according to claim 1 to 12,characterized in that the inductive coupling is realized by connecting astructure not yet in existence which is usable as an electric conductorloop.
 15. Configuration according to claim 1 to 12, characterized inthat the inductive coupling is realized by the steel belt of tires ofany kind.
 16. Configuration according to claim 1 to 12, characterized inthat the inductive coupling is realized by vulcanizing an additionalstructure which is usable as an electric conductor loop into tires ofany kind.